Chest compression apparatus for cardiac arrest

ABSTRACT

The invention is an apparatus for increasing intrathoracic pressure for resuscitating cardiac arrest patients. The apparatus comprises a flexible, substantially inelastic belt wrapped around the patient&#39;s chest and attached to a force converter. The force converter converts a downwardly directed force into a chestward resultant, which depresses the sternum, and two belt tightening resultants. The force converter comprises a pair of arm assemblies, each having a pair of spaced arms, which are pivotably mounted to a base. The base is positioned near the patient&#39;s sternum and the ends of the belt attach to one end of each arm assembly. The opposite, handle ends of the arm assemblies are depressed toward the chest causing tightening of the belt and compression of the chest cavity.

The present application is (1) a division of U.S. patent applicationSer. No. 09/059,497, filed Apr. 13, 1998 now U.S. Pat. No. 6,234,984,which is a continuation of U.S. patent application Ser. No. 08/573,465,filed Dec. 15, 1995, and issued as U.S. Pat. No. 5,738,637 on Apr. 14,1998, and (2) a continuation of U.S. patent application Ser. No.09/546,519, filed Apr. 11, 2000 now U.S. Pat. No. 6,325,771, which is acontinuation of U.S. patent application Ser. No. 09/059,497, filed Apr.13, 1998 now U.S. Pat. No. 6,234,984, which is a continuation of U.S.patent application Ser. No. 08/573,465, filed Dec. 15, 1995, and issuedas U.S. Pat. No. 5,738,637 on Apr. 14, 1998.

TECHNICAL FIELD

This invention relates broadly to the field of medical devices and morespecifically to an apparatus for increasing the blood flow bycompressing the chest cavity of a person suffering from cardiac arrest.

BACKGROUND ART

During cardiac arrest, it is desirable to generate blood flow byexternal means in order to maintain brain and heart viability.Traditionally, the external means of generating blood flow has beenmanual cardiopulmonary resuscitation (CPR). Using CPR, the rescuer tiltsthe patient's head back, lifts the chin to clear and straighten theairway, and depresses the sternum 1½ to 2 inches 15 times (at a rate of80 to 100 depressions per minute), after which the rescuer gives thepatient 2 full breaths. This 15 depressions and 2 breaths is repeatedcyclically.

Currently, the CPR research community believes that blood flow producedby external means can be explained by one, or a combination of two,theoretical mechanisms: the “cardiac pump” mechanism and the “thoracicpump” mechanism.

According to the cardiac pump mechanism, blood flow caused by externalmeans is due to direct mechanical compression of the heart. Duringcompression, blood is squeezed out of the heart chambers, and duringrelease of the compression (relaxation) blood flows into the heartchambers. Backflow of the blood is prevented by the valving of the heartand vessels.

According to the thoracic pump mechanism, blood is pumped by externalmeans as a result of the cyclical increase and decrease of intrathoracicpressure. During compression, the intrathoracic pressure rises, whichcauses blood to be forced out of the blood vessels and organs located inthe thorax, and the blood flows into the peripheral tissues. Duringrelease, blood flows back into the thorax via the normal venous return.In this method, backflow is prevented by the valving of the veins.

Most researchers believe that both mechanisms are active to some degree.However, the methods presently in use, and the devices currently in use,for promoting blood flow by the application of an external force aredirected toward only one of the two mechanisms. In order to maximizeblood flow, a device which takes advantage of both mechanisms is needed.

A variety of devices have been developed to increase blood and/or air flow in the chest cavity of a cardiac arrest patient.

U.S. Pat. No. 2,071,215 to Petersen shows a piston and cylinderarrangement attached to two ends of a girdle which encircles a patient'schest. The expansion or compression of a fluid in the piston andcylinder combination tightens and loosens the girdle to ventilate thelungs. This device is large and heavy, and is dependent upon acompressed fluid for driving power.

U.S. Pat. No. 3,425,409 to Isaacson et al. discloses an apparatus forcompressing the sternum by a downward force generated by a piston. Abelt is placed around the chest in order to minimize bodily damage, andair is applied to the air passages of the patient.

U.S. Pat. No. 5,287,846 to Capjon et al. shows an upper frame that restson a patient, whose back rests on a lower frame. Retractable strapsextend from the upper frame and attach to the lower frame. A hydrauliccylinder in the upper frame presses downwardly on the chest.

Barkalow, in U.S. Pat. No. 3,461,860, discloses a device using aPneumatic plunger to mechanically compress the sternum a predetermineddistance. A mechanical ventilator was added to this device in U.S. Pat.No. 4,326,507 to insure proper ventilation and increase the volume ofthe chest. This device was limited in its success due to complexitywhich requires trained personnel to use it.

A similar device was disclosed in U.S. Pat. No. 4,060,079 to Reinhold.This device is merely a similar portable unit.

Bloom, in U.S. Pat. No. 4,338,924, shows a sternum compression deviceusing an air cylinder to depress the chest of the cardiac arrestpatient. This device, like many others using a chest compression design,is large and is heavy.

Newman et al., in U.S. Pat. No. 4,424,806, show a pneumatic vest forgenerating a rise in thoracic pressure. This vest uses the “thoracicpump” concept of exerting greater force over a larger area under theassumption that if more major organs could be compressed and released,greater blood flow would occur. By releasing the compression force, thechest would return to its normal size and draw blood back into the majororgans. Positive blood flow would occur due to the one-way valves in thevascular network. The Newman device is not readily portable, in additionto having substantial complexity. In U.S. Pat. No. 4,928,674, Halperinet al. disclose a similar vest which is similarly not portable.

Lach et al., in U.S. Pat. No. 4,770,164, disclose a circumferential bandand take-up reel used to generate a rise in thoracic pressure. Althougheither manually or mechanically driven, this apparatus requires the useof a backboard for guiding the band around the chest.

The use of bands or belts to generate a rise in intrathoraciccompression for the purpose of assisting respiratory ailments isdisclosed in U.S. Pat. No. 651,962 to Boghean. This device is forperiodic loosening and tightening of the band around a patient's chestfor treating respiratory disease by regulating periods of breathing aswell as the size or depth of breath.

In U.S. Pat. No. 3,777,744, Fryfogle et al. disclose a breathing aidconsisting of a belt and a handle which tightens the belt for expellingexcessive residual air in the lungs.

Other devices known to the Applicants using circumferential bands forgenerating a compression force on the abdomen and lower chest to assistin compression of lungs for respiratory purposes include U.S. Pat. No.2,899,955 to Huxley, U.S. Pat. No. 3,368,581 to Glascock and U.S. Pat.No. 2,754,817 to Nemeth. Furthermore, the use of inflatable bladderspositioned around either the chest or the abdomen have been disclosed inU.S. Pat. No. 3,481,327 to Drennen, U.S. Pat. No. 3,120,228 to Huxley,U.S. Pat. No. 3,042,024 to Mendelson, U.S. Pat. No. 2,853,998 toEmerson, U.S. Pat. No. 2,780,222 to Polzin, U.S. Pat. No. 2,071,215 toPetersen, U.S. Pat. No. 4,424,806 to Newman and U.S. Pat. No. 4,928,674to Halperin.

U.S. Pat. No. 2,699,163 to Engström, shows a respirator device forventilating a patient's lungs.

U.S. Pat. No. 5,295,481 to Geeham shows a chest compression devicecomprising a T-shaped mechanical chest compression apparatus with asuction cup. The central shaft attached to the cup may be compressedbeyond the lips of the cup and bruise or otherwise injure the patientdue to the concentration of force on the patient by the shaft tip.

U.S. Pat. Nos. 4,397,306 to Weisfeldt et al. and 1,399,034 to Taplinshow large mechanical devices for compressing the chest of a cardiacarrest patient.

Szpur, in U.S. Pat. No. 5,407,418, discloses a power-driven, pulsatingcompressor apparatus for stimulating blood flow within vessels of aperson's foot or hand. The device periodically applies a concentratedforce against a localized region of the foot or hand.

In spite of the prior art, the need still exists for a device whicheffectively increases the flow of blood in the organs of a cardiacarrest patient. This device should be truly portable and useable by aperson of average strength and skill.

BRIEF DISCLOSURE OF INVENTION

The invention is an apparatus for increasing the flow of blood in apatient, for example a person suffering cardiac arrest. The apparatuscomprises a base contoured to seat near a central region of thepatient's chest. Also included are a manual actuator and a substantiallyinelastic belt which is for wrapping around the patient's chest. Theinvention further comprises a force converter mounted to the base. Theforce converter is connected to the actuator and has belt connectors forconnecting to opposite extremities of the belt. The force converter isfor converting a force manually applied to the actuator and directedtoward the chest into a chest compressing resultant. The chestcompressing resultant is directed through the base toward the chest. Theforce manually applied to the actuator is converted, in addition to thechest compressing resultant, into belt tightening resultants applied tothe belt connectors, and directed tangentially to the chest.

The invention contemplates the converter comprising first and secondassemblies. The first assembly has a pair of spaced, parallel armsrigidly connected at handle ends by a first hand-grippable handle. Thearms of the first assembly are further rigidly connected at opposite,belt ends by a first strut. The first assembly arms are pivotallymounted to the base at a first assembly fulcrum intermediate the handleand belt ends. The second assembly is substantially similar to the firstassembly and both assemblies are pivotally mounted to the base, forminga scissors arrangement. A force applied to the handle ends pivots thescissoring assemblies, which form a pair of levers. The strut ends ofthe assemblies are levered toward one another, tightening the beltattached to the is struts.

It is an objective of the present invention to provide an apparatushaving a flexible belt which wraps around the chest of a cardiac arrestpatient. The apparatus tightens the belt while depressing the chest, thecombination of which raises the intrathoracic pressure, enhancing bloodflow.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view in perspective illustrating an embodiment of thepresent invention in an operable position;

FIG. 2 is a side view in section illustrating the extreme positions ofthe arm assemblies of the embodiment of the present invention shown inFIG. 1;

FIG. 3 is a diagrammatic view illustrating a force diagram;

FIG. 4 is a diagrammatic view illustrating an alternative forceconverter;

FIG. 5 is a diagrammatic view illustrating an alternative forceconverter;

FIG. 6 is a diagrammatic view illustrating an alternative forceconverter;

FIG. 7 is a diagrammatic view illustrating an alternative forceconverter;

FIG. 8 is a diagrammatic view illustrating an alternative forceconverter;

FIG. 9 is a view in perspective illustrating an alternative embodimentof the present invention;

FIG. 10 is an end view in section illustrating a prime mover actuator aspart of the present invention;

FIG. 11 is a view in perspective illustrating an alternative embodimentof the present invention;

FIG. 12 is a diagrammatic view illustrating an alternative embodiment ofthe present invention;

FIG. 13 is a view in perspective illustrating an embodiment of thepresent invention;

FIG. 14 is an enlarged view in perspective of an embodiment of thepresent invention;

FIG. 15 is a side view in section illustrating the extreme positions ofthe arm assemblies of the embodiment of the present invention shown inFIG. 13;

FIG. 16 is a side view in section illustrating a sole of the base; and

FIG. 17 is a side view in section illustrating another sole of the base.

In describing the preferred embodiment of the invention which isillustrated in the drawings, specific terminology will be resorted tofor the sake of clarity. However, it is not intended that the inventionbe limited to the specific terms so selected and it is to be understoodthat each specific term includes all technical equivalents which operatein a similar manner to accomplish a similar purpose.

DETAILED DESCRIPTION

FIG. 1 shows the apparatus 10, which is an embodiment of the invention,in its operable position on and around a patient's chest 12. The base 14is a semi-rigid (preferably plastic) plate or block, preferably having acushioned outer surface contoured to seat against the central region ofthe patient's chest 12 near the sternum. The sole 92 of the base 14 isseated against the upper surface of the chest 12 and may have anadhesive pad 500 (shown in FIG. 16) or a suction cup 502 (shown in FIG.17) to adhere to the chest 12 so that pulling on the base 14 will causethe chest 12 to be pulled for decompression.

The base 14 contains a switch 70 and a pair of lights 72. Additionally,the base 14 contains a battery, a battery charge indicator and a soundgenerator (not visible in FIG. 1) which sound generator emits anaudible, periodic signal. The visible and audible signals indicate thefrequency to a rescuer of a compressive force he or she is to apply tothe apparatus 10. One or more of the audible or visible signals couldalso prompt the rescuer to apply ventilation. The base 14 also containsa force sensor, such as a strain gauge, and an indicator 74 whichindicates the force exerted on the chest 12 to warn the rescuer ofpotential injury due to excessive force. A limiter could be added tolimit some of the force applied to the patient to a specified maximum.

The first arm assembly 16 is made up of a pair of spaced, parallel arms22 and 24 which are made of high tensile strength, lightweight materialsuch as plastic. The second arm assembly 18 has substantially similarspaced, parallel arms 26 and 28. A pair of rods 37 and 38 rigidly fastenthe spaced parallel arms of the assemblies 16 and 18, respectively. Apair of manual actuators, which are preferably two cylindrical,hand-grippable handles 30 and 32, are rotatably mounted between thespaced, parallel arms of the first and second arm assemblies 16 and 18,around the rods 37 and 38, respectively. A pair of rod-like, preferablymetal struts 34 and 36 (strut 36 not visible in FIG. 1) rigidly mount tothe ends of the spaced arms, opposite the handles 30 and 32.

The rigid arm assemblies 16 and 18 pivot relative to one another aboutthe pivot pin 20, which is preferably a stainless steel bolt. The pin 20extends longitudinally through the base 14 and extends out of eachlongitudinal end to pivotally attach to each arm 22, 24, 26 and 28.

The arm assemblies 16 and 18 are arranged in a scissor-likeconfiguration. This configuration is designed to convert a small forceinto a larger force. This is done by the scissor-like configurationhaving a pair of levers with a common fulcrum, where the fulcrum islocated a distance from the center of the levers. A large displacementof the handles 30 and 32 causes a relatively small displacement of thestruts 34 and 36. In elementary physics, it is understood that workequals force times distance and the force applied to cause adisplacement at one end of a lever should equal the product of force anddisplacement at the opposite end of the lever. Conservation of workgives $\begin{matrix}{{F_{s}D_{s}} = {F_{h}D_{h}}} & \text{Equation~~1}\end{matrix}$

where the subscript s indicates the force or displacement at the struts34 and 36 and the subscript h indicates the force or displacement at thehandles 30 and 32. Solving Equation 1 for the force at the struts 34 and36 obtains $\begin{matrix}{F_{s} = {\frac{F_{h}D_{h}}{D_{s}}.}} & \text{Equation~~2}\end{matrix}$

The displacement at the struts 34 and 36 (D_(s) in Equation 2) willalways be smaller than the displacement at the handle (D_(h) in Equation2). By separating the displacement part of Equation 2 in parenthesis,the following is obtained: $\begin{matrix}{F_{s} = {{F_{h}\left( \frac{D_{h}}{D_{s}} \right)}.}} & \text{Equation~~3}\end{matrix}$

Since the displacement at the struts is smaller than the displacement atthe handles, the displacement portion of Equation 3 will be a numbergreater than 1 which, when multiplied by the force at the handles, willobtain a force at the struts which is greater than the force at thehandles. It is this greater force at the struts 34 and 36, effected bythe force applied to the handles, which is used to artificially induceor enhance blood flow in a patient.

The pivoting motion of the arm assemblies 16 and 18 is a simple andreliable action which virtually any person can effectuate. Doing sorequires a small force, and creates a larger force that is to be appliedto a patient's chest 12. The force at the struts 34 and 36 could not begenerated by an average person for the time period required to treat acardiac arrest patient, without the help of a mechanical device.

Two stainless steel stroke limiters 52 and 54 are pivotally mounted tothe arms 22 and 24 and slidingly attach to the arms 26 and 28. Thelimiters 52 and 54 serve the purpose of limiting the relative pivotingdisplacement of the assemblies 16 and 18 by mechanically restrictingtheir movement. Unlimited displacement between the two assemblies 16 and18 could result in an excessive compression force on the chest 12 whichcould injure the patient.

An alternative to the arm assemblies 16 and 18 shown in FIG. 1 is thearm assemblies 416 and 418 shown in FIG. 13. The arm assemblies 416 and418 are made up of the spaced, parallel arms 422, 424, 426 and 428,respectively. The curved shape of the arms 422-428 making up the armassemblies 416 and 418 has been found to be more advantageous than theangled shape of the arms making up the arm assemblies 16 and 18 shown inFIG. 1. The advantage is found primarily in the means for limiting therelative displacement of the arm assemblies 416 and 418. The preferredmeans for limiting the relative displacement is shown in greater detailin FIG. 14.

As the arms 422 and 426, shown in FIG. 14, pivot about the commonfulcrum located at the pivot pin 430, they pivot toward the stop pin432. The stop pin 432 extends through one of three holes formed in anupright 434 which extends rigidly from the base 414. The arm 422 hasthree shoulders 440, 442, and 444 which face the stop pin 432. The arm426 has three similar shoulders 446, 448 and 450. In their relaxedposition shown in FIG. 14, the arms 422 and 426 have gaps of apredetermined distance between corresponding shoulders. For example, thegap between shoulder 442 and shoulder 448 is a predetermined size whenthe arms 422 and 426 are in their relaxed position. As the arms 422 and426 are pivoted toward one another, the gaps between the shouldersdecrease in size. In order to insure that the gap between a particularpair of shoulders does not decrease below a specified minimum, the stoppin 432 is placed in one of the three holes 452, 454 or 456 formed inthe upright 434. Each hole has an axis which extends into a particulargap. Since the three gaps between the six shoulders 440-450 are ofdifferent length, the position of the stop pin 432 in the upright 434will affect the distance the arms 422 and 426 can travel until twoassociated shoulders seat against the stop pin 432, restricting furtherdisplacement.

For example, FIG. 15 shows the arm assemblies 416 and 418 in theirrelaxed positions and in phantom in an extended position. In theextended position, when the stop pin 432 is positioned in the hole 456of the upright 434, the shoulders 440 and 446 seat against the stop pin432 to limit the extension of the arm assemblies 416 and 418.

The belt 40, which extends around the front, sides and back of thechest, is substantially inelastic and flexible. A plurality of indicia50 is imprinted on the exposed surface of the belt 50. The belt 40attaches to the strut 34 on one side of the chest 12, and extends arounda major portion of the circumference of the chest 12 to attach to theother strut 36. When the assemblies 16 and 18 pivot around the pivot pin20, the belt 40 is tightened by the struts 34 and 36 to which the belt40 attaches.

Although the belt 40 is described as extending around the front, sidesand back of the chest, the belt may be made up of two or more componentparts, such as a pair of belts. This pair of belts could extend fromattachment to the struts 34 and 36, extending downwardly past the sidesof the patient's chest to rigid attachment to a board which spans thewidth of the back of the chest. Therefore, “a belt wrapped around thechest” can be made up of two or more belt components which extend aroundportions of the chest circumference in combination with other rigid orflexible components.

The relaxed and mid-actuated positions of the arms of the apparatus 10are shown in FIG. 2. The first and second assemblies 16 and 18 are shownin their relaxed position and (in phantom) at the mid-point of theiractuated position. The assemblies 16 and 18 are biased into the relaxedposition by a spring (not shown) which could be a torsion springextending around pin 20 and connecting to the assemblies 16 and 18. Thehandle ends 80 and 82 of the arms 22 and 26 pivot along an arcuate pathdownwardly and away from each other, and the belt ends 84 and 86 of thearms 22 and 26 pivot upwardly and toward one another in an arcuate pathsubtending the same angle as the handle ends 80 and 82. The beltextremities 88 and 90 (which are the looped ends of the belt 40 whichattach to the struts 34 and 36) follow the belt ends 84 and 86 of thearms to an upward and more. proximally spaced position. Since the belt40 is substantially inelastic, its circumference will decrease under theforce applied to it by the struts 34 and 36, thereby tightening the belt40 around the chest 12.

The belt 40 extends through slots 44 formed in a backboard 42 which,when in use, is positioned beneath the chest 12 of the patient. The belt40 preferably seats against a sliding mechanism 43 which permits slidingof the belt 40 along the length of the chest 12 for positioning of thebelt 40 on the chest 12. The backboard 42 is made of a strong,lightweight material such as plastic and is wide enough to span thewidth of the chests of a large majority of the population. The backboard42 has a padded, raised portion 46 which elevates the patient's neckabove his head for opening the breathing passages, and the backboard 42preferably has handles 250 and 252 (shown in FIG. 9) for carrying thebackboard 42 with or without a patient lying on it. The backboard 42,the attached belt 40 and the assemblies 16 and 18, are all hung on awall by extending hooks through the handles 250 and 252 or by some otherconventional hanging means, and may be hinged near the center forfolding during storage.

An oxygen tank 100 and a mask 102 are shown in hidden lines in FIG. 2 ascontained within a chamber 104 formed in the backboard 42. A gauge 103,indicating the amount of oxygen in the tank 100, is visible through theport 101. The raised portion 46 of the backboard 42 is suited to theformation of a cylindrical chamber 104 in which the oxygen tank 100 canbe easily stored. If needed, the mask 102 can be withdrawn from thechamber 104 and placed over the patient's mouth for enhanced ventilationof the patient's lungs.

The apparatus 10 is operated in the following manner, referring to FIGS.1 and 2. The victim is placed onto the backboard 42 with his or herchest 12 in the position shown in FIG. 1. The back of the patient'schest 12 seats against the surface of the backboard 42 with thepatient's neck resting on the raised portion 46 and his head lying onthe horizontal surface on which the backboard 42 lies, such as a floor.The base 14 of the apparatus 10 is placed at approximately the center ofthe patient's chest 12 near the sternum. The belt 40 is then extendedupwardly from the backboard 42, between the arms and chest 12, andaround opposite sides of the chest 12 to match the relaxed contour ofthe chest 12. The belt 40 is positioned as high on the chest 12 and ashigh under the underarms as possible.

The belt 40 is next extended around the struts 34 and 36, passing firstbetween each strut 34 and 36 and the base 14. The base 14 is moreexactly positioned near the center of the chest 12 by matching theindicia 50 on the belt 40 on opposite sides of the base 14. The indicia50 are alphanumeric characters spaced equally along the length of thebelt 40 in a preferably identical arrangement at both ends of the belt40. The indicia could, of course, be colored bands or other symbols.

Once the belt 40 extends around the struts 34 and 36, the ends of thebelt 40 are folded back over onto the portion of the belt 40 contactingthe chest 12 and are attached thereto by fasteners. Before fastening,though, the indicia 50 at both struts 34 and 36 must match. For example,the number “3” is shown as the highest number on the belt 40 visible inFIG. 1. In this example, the same number (“3”) should be the highestnumber visible at both struts 34 and 36, which indicates that an equallength of the belt 40 extends from the backboard 42 to the strut 34 asto the strut 36, and therefore that the base 14 is centered on the chest12.

After fastening the belt 40 to the struts 34 and 36, is the strokelimiter pins 60 and 62 extend into the holes 1 and 4 in the arms 26 and28. Since the number “3” is the highest visible number on the belt 40,the limiter pins 60 and 62 are placed in the distal of the six holes 1-6in arms 26 and 28. If the number “2” were the highest number visible onthe belt 40, the center holes 2 and 5 of the six holes 1-6 on the pivotarms 26 and 28 would be used, since the number “2” would indicate alarger chest circumference than when “3” is the highest visible number.The stroke when the number “2” is the highest visible number is greaterthan when “3” is the highest visible number. This means for a largerchest circumference, the apparatus would be permitted to cause greaterdisplacement of the chest 12.

If the arm assemblies 416 and 418 shown in FIG. 13 are used rather thanthe arm assemblies 16 and 18 shown in FIG. 1, then the highest numbervisible on the belt 40 would indicate the positioning of the stop pin432 in the upright 434. For example, since the number 3 is the highestnumber visible on the belt 40 in FIG. 1, the stop pin 432 would beplaced in the hole 456 which has the indicium “3” next to it. Theindicium “3” is visible in FIG. 15, but only the indicia “1” and “2” canbe seen in FIGS. 13 and 14.

Once the apparatus 10 is positioned with the belt 40 around the chest12, the base 14 is centered and the limiters 52 and 54 are in thecorrect position for the visible indicia 50 on the belt 40, the rescuerdepresses the switch 70. This causes the lights 72 to begin emitting aperiodic, visible signal and the base 14 to emit a periodic, audiblesignal in synchronization with the lights 72. The rescuer then gripshandles 30 and 32 with his or her hands and, with a downwardly directedforce toward the chest 12, pushes the handles 30 and 32, pivoting themabout the pivot pin 20, thereby pivoting the arms 22, 24, 26 and 28through arcuate paths about the pin 20. This pivoting motion causes thestruts 34 and 36 at the opposite ends of the arms from the handles 30and 32 to pivot about the pivot pin 20 in a direction away from thechest 12, but with a smaller displacement than the handles 30 and 32.Pivoting of the struts 34 and 36 draws the ends of the belt 40 closertogether, thereby tightening the belt 40 around the chest 12. Since thebelt 40 is inelastic, tightening of the belt 40 compresses the chest 12.The arcuate motion of the handles 30 and 32 is limited to a maximumdisplacement by the stroke limiters 52 and 54, when the pins 60 and 62contact the ends of the slots 64 and 66. The force on the handles 30 and32 is released and then exerted again by the rescuer after the handles30 and 32 have returned to their original positions.

By cyclically depressing with a downwardly directed force, and releasingthe handles 30 and 32 (preferably in phase with the lights 72), therescuer cyclically tightens and loosens the belt 40 around the patient'schest 12. The base 14 concentrates some of the tightening force of thebelt in the chest 12 center and prevents pinching of the chest by thescissor-like assemblies 16 and 18. The belt 40 tightening around thechest 12 represents the “thoracic pump” method of artificially inducingblood flow in a cardiac arrest patient by applying a circumferentialcompressive force to a large area. The large force is from the leveragecreated by the scissor-like assemblies 16 and 18, and the large area isthe circumference of the chest 12.

As the first assembly 16 and the second assembly 18 are forceddownwardly toward the chest, the base sole 92 is forced downwardly alonga path directed into, and preferably perpendicular to, the chest surfaceby the downwardly directed force on the handles 30 and 32. Therefore,each depression of the first and second assemblies 16 and 18 results ina downward compression of the center of the chest by the base 14. Thisis the “cardiac pump” method of inducing blood flow by compressing theheart between the spine and the sternum.

Compressing the organs using the present invention takes advantage ofboth the “thoracic pump” (belt tightening and loosening) and “cardiacpump” (chest depression by the base 14) methods to convey blood throughthe blood vessels and, upon release, draw blood back into the organs.Upon each increase in pressure, the blood is compressed out of theorgans (and air out of the lungs) and along the vascular system. Uponrelease, other blood is pulled in. Since the veins have a series ofone-way valves, the periodic raising and lowering of thoracic pressurewith the present invention creates an artificial blood flow supplyingnecessary elements to the vital organs, such as the brain, whichincreases the patient's chances of survival.

The pivoting assemblies 16 and 18 comprise a force converter whichconverts the downwardly directed chest compressing force applied to thehandles 30 and 32 into multiple resultant forces. These resultant forcesinclude a downwardly directed force applied from the base 14 into thechest 12 and two equal tangential forces applied by the struts 34 and 36to the belt 40. The forces are applied tangentially to the chest 12since the belt 40 wrapped around the chest 12 and pulled taut must betangential to the chest 12 surface if it contacts the chest at the chestsides as shown in FIG. 1. The assemblies 16 and 18 comprise the forceconverter which is a device that converts the force manually applied tothe handles 30 and 32, and directed toward the chest 12, into theresultants described above (specifically, a chest compressing resultantand a pair of belt tightening resultants).

A converter for converting the above described applied force into theresultants includes all equivalents to the preferred force converter. Aconverter need not merely redirect a specific force but could amplify,reduce or signal a device to generate other forces, by the applicationof a force.

The force necessary to generate sufficient pressure in the chest cavityto create blood flow can be generated by an average person if a deviceutilizes an applied force correctly. In the position in which a cardiacarrest patient is normally found, a rescuer cannot normally, withoutleverage, generate a downward force into the patient's chest sufficientto generate the necessary intrathoracic pressure without the risk ofinjury. The apparatus of the present invention uses the force which anaverage person can apply and converts the applied force into resultantforces in the directions needed while limiting the maximum displacementof the chest to prevent injury.

The force converter described above can be considered as a free bodyshown in FIG. 3 having an applied force 112 directed downwardly onto theconverter 110. An opposite force 114 is applied by the chest against theconverter 110 as a reaction to the opposite force 112. The tangentialforces 116 and 118 are the forces of the belt, extendingcircumferentially around the chest, pulling on the converter 110. Theconverter 110 converts the downwardly directed force 112 into resultantforces 120, 122, and 124. The resultant force 120 is directed into thechest along a direction similar to the applied force 112. The resultantforces 122 and 124 apply a tangential tension force to the belt which istangential to the patient's chest.

The preferred embodiment of the present invention is one device theApplicants have found advantageous for converting the downward force 112into the three resultant forces 120, 122 and 124. The Applicants knowthat many apparatuses are equivalent to, and could be substituted for,the preferred apparatus to provide the force conversion described inassociation with FIG. 3. Although it is impossible to list everymechanical device which one skilled in the art will know can convert anapplied force into the desired resultant forces, some of the manyequivalents are described herein. However, this is not an exhaustivelist, and other equivalents exist as will become apparent to thoseskilled in the art.

FIG. 4 shows a diagrammatic illustration of a cam 140 and a pair of camfollowers 142 and 144. Upon the application of a downward force by thecam 140 onto a pair of inclined surfaces 143 and 145, the follower 142will slide rightwardly and the follower 144 will slide leftwardly,thereby exerting forces on the belt ends attached thereto, tighteningthe belt. The cam 140 will slide down the inclined surfaces of followers142 and 144, and upon reaching the horizontal surfaces 146 and 148, willstop abruptly—exerting a downward force onto the surface beneath thefollowers 142 and 144, which could be the base of the present invention.The apparatus of FIG. 4 is equivalent to the preferred force converterapparatus.

FIG. 5 shows a diagrammatic illustration of a first eccentric 150 and asecond eccentric 152 pivotally mounted to a base 154. A manual actuator156 attaches to a second pivot on each eccentric. A pair of belt ends158 and 160 wrap around the eccentrics 150 and 152, respectively. Uponthe application of a downwardly directed force on the actuator 156, theeccentrics 150 and 152 pivot about the pivot points, exerting a force onthe belt ends 158 and 160 causing a tightening of the belt. Theeccentrics 150 and 152 will, upon a sufficient downwardly directed forceon the actuator 156, impact upon the base 154, exerting a downwardlydirected force on the base 154 as in the preferred embodiment. Theapparatus of FIG. 5 is equivalent to the preferred embodiment.

FIG. 6 illustrates a diagrammatic illustration of another equivalent tothe preferred embodiment including an actuator 170 to which a downwardlydirected force is applied. The actuator 170 has a two-sided toothedsurface 172 which inter-engages with a pair of gears 174 and 176. Gears174 and 176 are pivotally mounted to a base 178 and a pair of belt ends180 and 182 wrap around a pair of drums 184 and 186 at each of the gears174 and 176. The toothed surface 172, upon a downwardly applied force tothe actuator 170, causes the inter-engaging gears 174 and 176 to rotate,thereby applying a force to the ends 180 and 182 of the belt. Theactuator 170 impacts the base 178 upon being actuated to a certainextremity, thereby exerting a downwardly directed force to the base 178as in the preferred embodiment.

Another alternative, mechanical apparatus 260 which is equivalent to thepreferred embodiment is shown in FIG. 11. The apparatus 260 has a pairof pivoting arms 262 and 264 which pivot about a pivot axis 266 on abase 268. A belt 270 attaches at opposite longitudinal ends to the arms262 and 264. The base 268 is positioned on a patient's chest 272, thebelt 270 is extended circumferentially around the chest 272 and attachedto the handles 262 and 264. A downwardly directed force is applied tothe handles 262 and 264, tightening the belt 270 as the arms 262 and 264pivot about the pivot pin 266. In addition to the tightening of the belt270, the base 268 is forced downwardly into the chest 272.

FIG. 12 shows a two-chamber device having a base 300 and two pivotingarms 302 and 304. Two springs 306 and 308 keep two arms 302 and 304biased upwardly within the chamber 310. A plunger 312 is biased awayfrom the chamber 310 by a spring 314. The belt 316 is attached to thearms 302 and 304. Upon downward compression of the plunger 312, the arms302 and 304 are rotated counterclockwise and clockwise, respectively.This rotation tightens the belt 316 and a patient's chest is compressedwith the tightened belt 316 and with the base 300, especially when theplunger 312 reaches the lower limit of the chamber 310.

Many illustrations show equivalent substitute devices for converting anapplied force into the desired resultant forces. Most of those describedabove show purely mechanical equivalents to the preferred embodiment. Asa person skilled in the mechanical arts will quickly find, there aremany other different substitutes for the preferred embodiment. Thesedevices are equivalent to the preferred embodiment or one of thealternatives described above and shown in the drawings. In addition topurely mechanical alternatives to the preferred embodiment, it is ofcourse possible to combine mechanical, electrical, hydraulic and manyother elements to arrive at an equivalent substitute for the preferredembodiment. These combination equivalents are discussed below.

In FIG. 7 a mechanical and electrical combination equivalent is showndiagrammatically including an actuator 200 and an electric motor 202attached to a base 204. The motor 202 has a pair of belt ends 206 and,208 attached to a driveshaft 210. Upon depression of the actuator 200, apressure-sensitive switch 212 actuates the motor 202, rotating thedriveshaft 210 and exerting a linear force on the belt ends 206 and 208.As the force is applied to the actuator 200, this downwardly directedforce is transmitted through the base 204 to the patient's chest whichlies directly beneath the base 204. The embodiment of FIG. 7 isequivalent to the preferred embodiment.

FIG. 8 shows still another equivalent to the present invention in adiagrammatic illustration including a hydraulic cylinder 220, fluidlines 222 and 224, and pistons 226 and 228 slidingly mounted within thecylinder 220. The belt ends 230 and 232 are mounted to the pistons 226and 228. Upon actuation of an actuator 234, hydraulic fluid is forcedinto the hydraulic cylinder 220 forcing the pistons 226 and 228 towardone another longitudinally, thereby exerting a force on the belt ends230 and 232. The actuation of the actuator 234 is accomplished by adownwardly directed force which exerts a similar force to a patient'schest lying directly beneath the hydraulic cylinder 220.

The actuator 234 could be attached to a central piston which compressesa fluid within a hydraulic cylinder. Upon actuation of actuator 234, thehydraulic fluid within the cylinder is compressed and is conveyedthrough the lines 222 and 224 and the pistons 226 and 228 are driveninwardly as described above. This embodiment is also equivalent to thepreferred embodiment.

It is possible to attach a power unit, such as a prime mover, to theapparatus 10 which could function as an actuator to apply a lateralforce to the arm assemblies 16 and 18 to actuate them automatically andin regular, periodic intervals. As shown in FIG. 9, the power unit 254has a cable 256 which attaches to a belt 258. The device providing amechanical force to the belt 258 may be located in the power unit 254and the cable 256 is then rotatingly driven or longitudinally,reciprocatingly driven to tighten and loosen the belt 258.Alternatively, the actuator which tightens and loosens the belt 258could be located beneath the belt 258 and the cable 256 would merelyconvey electrical power or fluid pressure to the actuator. The powerunit 254 may use computer controls to time the application of force.

An example of a power unit 280 applying a force which tightens a belt282 and depresses a base 284 is shown in the development of anotherperson appearing in FIG. 10. As the rod 286 extends inwardly andoutwardly of the power unit 280, the base 284 is displaced upwardly anddownwardly, depressing the chest 288 as described with the preferredembodiment. Furthermore, this same mechanical motion of the rod 286tightens and loosens the belt 282 as with the preferred embodiment.

In order to ensure that the patient's lungs are allowed to expand asmuch as desired, it may be necessary to include a full-release indicatorwith the present invention. This indicator should have some means foralerting the rescuer when full release of the tension on the belt hasnot occurred. This indicator may include a limit switch, a magnet reedrelay or contacts on the base 14 against which the arm assemblies 16 and18 rest in their relaxed position.

Instead of an indicator of full release, a mechanism could be added tothe arm assemblies 16 and 18 for preventing the application of force tothe handles 30 and 32 until full release (and return to the relaxedposition) has occurred. A ratchet mechanism having discreet spacingscould be used for this purpose. Additionally, such mechanisms arecommonly found on electrical crimping tools for loose terminals.

It is possible to build into the force converter a mechanism for storingand suddenly releasing energy during the application of a downwardforce. The sudden release would be actuated during the withdrawal of thedownward force, applying a short duration, high intensity force to thechest rather than a long duration application of force as with thepreferred embodiment.

It is preferred that the apparatus which rests on the top of a patient'schest be as light in weight as possible. The reason for this is thatafter the patient's chest has been fully compressed, any weight whichrests on top of the chest will tend to resist decompression of the chestonce the compression force is removed. Reducing this weight minimizesthe amount of unwanted compression during release and decompression ofthe chest.

The adhesive pad 500 shown in FIG. 16 could contain an electrode whichis electrically attached to a voltage generating device as isconventionally known. The adhesive pad 500 could be used in combinationwith one or more electrodes 504 interposed along the length of the belt506 or embedded in the backboard 508. These electrodes are used in theconventional manner to induce a current through the chest 510 which isused for defibrillating the patient's heart. Any combination of two ormore electrodes can be used to induce a current to defibrillate theheart.

The electrodes 504 can be interposed at multiple positions along thelength of the belt 506 or in the backboard 508, but there willpreferably be a minimum of one electrode on the base 512 (such as theadhesive pad 500 which functions as an electrode) in addition to atleast one other electrode 504. The reason it is desirable to have anelectrode at least on the base 512 is that at the furthest extent ofcompression of the chest 510, the distance between the anterior andposterior outer surfaces of the chest 510 will be at a minimum, and thebase 512 will be positioned closer to the heart than at any other pointin the whole compression/decompression cycle. At this point there is aminimum of resistance to the flow of current which gives the greatestcurrent flow through the heart with the least likelihood of injuring thepatient's chest 510 tissue.

The electrodes 504 can be positioned not only circumferentially aboutthe chest 510, but can also be positioned at the same circumferentiallocation but at various longitudinal spacings.

It is preferred that a means be adapted to limit the travel of theassemblies 416 and 418 shown in FIG. 13 to only permit the assemblies416 and 418 to move equal amounts relative to the base. It isundesirable for one assembly to move to one side more than the otherassembly, since this causes an imbalance in the application of force,which may result in injury to the patient. The injury arises when agreater force is applied to one edge of the base than the opposite. Thiscan occur if one of the two assemblies 416 and 418 moves a substantiallygreater distance than the other assembly. One means for limiting theirrelative motion is a pin in aligned slots in the arms. Another is a gearmechanism connected to both assemblies 416 and 418.

While certain preferred embodiments of the present invention have beendisclosed in detail, it is to be understood that various modificationsmay be adopted without departing from the spirit of the invention orscope of the following claims.

What is claimed is:
 1. An apparatus for increasing the flow of blood ina patient, the apparatus comprising: (A) a base contoured to seat near acentral region of a patient's chest; (B) an actuator; (C) asubstantially inelastic belt configured to wrap around said patient'schest; and (D) a force converter, mounted on said base, coupled to saidactuator, and having two belt connectors coupled to opposite extremitiesof said belt for converting a force directed toward said chest andapplied to said actuator into belt tightening resultants appliedsubstantially equally to said two belt connectors directed substantiallytangentially to said chest to cause substantially equal movement of saidtwo belt connectors in the directions to tighten said belt around saidpatient.
 2. The apparatus of claim 1 wherein said actuator is a manualactuator and said force is manually applied to said actuator.
 3. Theapparatus of claim 2 wherein said force converter also converts saidforce applied to said actuator and directed toward said chest into achest compressing resultant directed through said base towards thechest.
 4. The apparatus of claim 3 wherein said manual actuatorcomprises at least one hand grippable handle.
 5. The apparatus of claim3 further comprising defibrillating means coupled to said base.
 6. Theapparatus of claim 5 further comprising first and second spacedelectrodes mounted to said apparatus for contacting two spaced outerchest surfaces with said first electrode being mounted to a base outer,chest-contacting surface and said second electrode being mounted to anapparatus chest-contacting surface which is spaced from said firstelectrode.
 7. The apparatus of claim 3 further including a rigid,substantially planar backboard and wherein said belt includes twoseparate portions with one end of each of said portions attached to saidboard.
 8. The apparatus of claim 7 wherein the other ends of saidportions of said belt are attachable to and removable from said forceconverter.
 9. The apparatus of claim 3 further comprising first andsecond spaced electrodes mounted to said apparatus for contacting twospaced outer chest surfaces with said first electrode being mounted to abase outer, chest-contacting surface and said second electrode beingmounted to an apparatus chest-contacting surface which is spaced fromsaid first electrode.
 10. The apparatus of claim 3 wherein said actuatormoves said two belt connectors in said direction to tightens said beltaround said patient proportionally to the magnitude of the movement ofsaid actuator toward said chest.
 11. The apparatus of claim 10 whereinsaid converter includes a cam coupled to said actuator and a camfollower coupled to said belt connectors, said force applied to saidconverter causing said cam to move along said cam follower in a mannerto move said two belt connectors in said directions to tighten said beltaround said patient.
 12. The apparatus of claim 10 wherein saidconverter includes a toothed surface, coupled to said actuator, andgears, coupled to said belt connectors and engaged with said toothedsurface, said force applied to said converter causing said toothedsurface to move along said gears in a manner to move said two beltconnectors in said directions to tighten said be around said patient.13. The apparatus of claim 3 wherein said actuator moves said two beltconnectors in said directions to tighten said belt around said patientnonproportionally to the magnitude of the movement of said actuatortoward said chest.
 14. The apparatus of claim 13 wherein said forceconverter includes first and second eccentrics each pivotally mounted atfirst pivots on said base and pivotally mounted at second pivots to saidactuator, and having a belt connector coupled to one of said oppositeextremities of said belt, said force applied to said converter causingsaid eccentrics to move in a manner to move said two belt connectors insaid directions to tighten said belt around said patient.
 15. A methodof CPR treating patients comprising: (A) seating a base of a blood flowincreasing apparatus on a patient's chest near a central region of saidchest; (B) wrapping a belt with first and second opposite extremitiesaround said patient's chest; (C) fastening to said apparatus any of saidextremities of said belt not already fastened to said apparatus; (D)applying a force, directed toward said chest, to an actuator coupled toa converter coupled to said base and said first and second oppositeextremities of said belt; (E) converting said force into belt tighteningresultants directed substantially tangentially to said chest and appliedsubstantially equally to said two belt extremities; and (F) moving saidtwo belt extremities substantially equally in the directions to tightensaid belt around said patient.
 16. The method of claim 15 furtherincluding periodically repeating steps (D) to (F).
 17. The method ofclaim 16 wherein said force is manually applied to said actuator. 18.The method of claim 17 further including converting said force appliedto said actuator and directed toward said chest into a chest compressingresultant directed through said base towards the chest.
 19. The methodof claim 18 wherein applying said force includes manually gripping ahand grippable handle.
 20. The method of claim 18 further comprisingdefibrillating the chest of said patient undergoing CPR.
 21. The methodof claim 20 further including contacting two spaced outer chest surfaceswith a first electrode and a second electrode.
 22. The method of claim18 wherein said belt includes two separate portions and furtherincluding attaching one end of each of said portions to a rigid,substantially planar backboard.
 23. The method of claim 22 furtherincluding attaching the other ends of said portions of said belt to saidapparatus.
 24. The method of claim 18 further including contacting twospaced outer chest surfaces with a first electrode and a secondelectrode.
 25. The method of claim 18 wherein said two belt extremitiesare moved in said direction to tighten said belt around said patientproportionally to the magnitude of the movement of said actuator towardsaid chest.
 26. The method of claim 15 wherein said converter includes acam engaged with a cam follower coupled to said converter and said firstand second opposite extremities of said belt, and further includingconverting said force into motion of said cam against said cam followerto move said cam follower in said directions to produce belt tighteningresultants directed substantially tangentially to said chest.
 27. Themethod of claim 15 wherein said converter includes a toothed surfaceengaged with gears coupled to said converter and said first and secondopposite extremities of said belt and further including converting saidforce into motion of said toothed surface against said gears to movesaid gears in a directions to produce belt tightening resultantsdirected substantially tangentially to said chest.
 28. The method ofclaim 18 wherein said two belt extremities are moved in said directionsto tighten said belt around said patient nonproportionally to themagnitude of the movement of said actuator toward said chest.
 29. Themethod of claim 28 wherein said converter first and second eccentricseach pivotally mounted at first pivots on said base and pivotallymounted at second pivots to said actuator and further includingconverting said force into motion of first and second eccentrics in adirections to produce belt tightening resultants directed substantiallytangentially to said chest.
 30. An apparatus for increasing the flow ofblood in a patient, the apparatus comprising: (A) a base contoured toseat near a central region of a patient's chest; (B) an actuator; (C) asubstantially inelastic belt configured to wrap around said patient'schest; and (D) a force converter, mounted on said base, coupled to saidactuator, and having two belt connectors coupled to opposite extremitiesof said belt, for converting a force applied to said actuator anddirected toward said chest into belt tightening resultants directedsubstantially tangentially to said chest to cause movement of said twobelt connectors in the direction to tighten said belt around saidpatient, said converter including a cam coupled to said actuator and acam follower coupled to said belt connectors, said force applied to saidactuator causing said cam to move along said cam follower in a manner tomove said two belt connectors in said direction to tighten said beltaround said patient.
 31. The apparatus of claim 30 wherein said actuatoris a manual actuator and said force is manually applied to saidactuator.
 32. The apparatus of claim 31 wherein said force converteralso converts said force applied to said actuator and directed towardsaid chest into a chest compressing resultant directed through said basetowards the chest.
 33. The apparatus of claim 32 further comprisingdefibrillating means coupled to said base.
 34. The apparatus of claim 33further comprising first and second spaced electrodes mounted to saidapparatus for contacting two spaced outer chest surfaces with said firstelectrode being mounted to a base outer, chest-contacting surface andsaid second electrode being mounted to an apparatus chest-contactingsurface which is spaced from said first electrode.
 35. The apparatus ofclaim 32 further comprising first and second spaced electrodes mountedto said apparatus for contacting two spaced outer chest surfaces withsaid first electrode being mounted to a base outer, chest-contactingsurface and said second electrode being mounted to an apparatuschest-contacting surface which is spaced from said first electrode. 36.The apparatus of claim 32 wherein said force converter converts saidforce applied to said actuator to cause said cam to move along said camfollower in a manner to move said two said two belt connectorssubstantially equally in said directions to tighten said belt aroundsaid patient.
 37. The apparatus of claim 32 wherein said actuator movessaid two belt connectors in said directions to tighten said belt aroundsaid patient proportionally to the magnitude of the movement of saidactuator toward said chest.
 38. The apparatus of claim 32 wherein saidactuator moves said two belt connectors in said directions to tightensaid belt around said patient nonproportionally to the magnitude of themovement of said actuator toward said chest.
 39. A method of CPRtreating patients comprising: (A) seating a base of a blood flowincreasing apparatus on a patient's chest near a central region of saidchest; (B) wrapping a belt with first and second opposite extremitiesaround said patient's chest; (C) fastening to said apparatus any of saidextremities of said belt not already fastened to said apparatus; (D)applying a force, directed toward said chest, to an actuator coupled toa cam of a converter coupled to said base, said cam being engaged with acam follower coupled to said converter and said first and secondopposite extremities of said belt; (E) converting said force into motionof said cam against said cam follower to move said cam follower in adirection to produce belt tightening resultants directed substantiallytangentially to said chest and applied substantially equally to said twobelt extremities; and (F) moving said two belt extremities in thedirections to tighten said belt around said patient.
 40. The method ofclaim 39 further including periodically repeating steps (D) to (F). 41.The method of claim 40 wherein said force is manually applied to saidactuator.
 42. The method of claim 41 further including converting saidforce applied to said actuator and directed toward said chest into achest compressing resultant directed through said base towards thechest.
 43. The method of claim 42 further comprising defibrillating thechest of said patient undergoing CPR.
 44. The method of claim 43 furtherincluding contacting two spaced outer chest surfaces with a firstelectrode and a second electrode.
 45. The method of claim 42 furtherincluding contacting two spaced outer chest surfaces with a firstelectrode and a second electrode.
 46. The method of claim 42 whereinsaid force is converted into motion of said cam against said camfollower in said direction to produce said belt tightening resultantsdirected substantially tangentially to said chest and appliedsubstantially equally to said two belt extremities and to move said twobelt extremities substantially equally in said directions to tightensaid belt around said patient.
 47. The method of claim 42 wherein saidtwo belt extremities are moved in said directions to tighten said beltaround said patient proportionally to the magnitude of the movement ofsaid actuator toward said chest.
 48. The method of claim 42 wherein saidtwo belt extremities are moved in said directions to tighten said beltaround said patient nonproportionally to the magnitude of the movementof said actuator toward said chest.